[Elecraft] Re: Elecraft Digest, Vol 16, Issue 31 -- Toroid Use and History

[Wa6bfh at aol.com]

What is the theory, or greater breadth of physics about toroid  transformers? 
When did they come about, and what was the logic in replacing “C”  or “E” 
frames (for non-RF applications).
 
I had an old Uti-Com Communications radio that used a toroid switcher, and  
many other aspects of the radio were of quite modern design for its time frame. 
 It even used a strip-line of 6360’s as buffer/multipliers, one as the 
driver,  and two as the final.
 
I saw a transformer design once for an “intrinsically safe” isolator for  “DC
” analog lines, and the toroids used in this “phased switcher/rectifier” 
were  covered with ferrite covers. I also seem to remember that design in the 
Western  Electric 247B tone decoder.